Utility scale electric energy storage system

ABSTRACT

A potential energy storage system incorporating multiple track mounted shuttle units having motor/generator drive bogies and structure with an integral transfer mechanism for removably carrying energy storage masses from a first lower elevation storage yard to a second higher elevation storage yard employing excess energy from the electrical grid driving the motors, removing the masses in the second storage yard for energy storage, retrieving the masses and returning the masses from the second storage yard to the first storage yard recovering electrical energy through the generators.

REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. provisional patent applicationSer. No. 61/233,052 filed on Aug. 11, 2009 by William R. Peitzke andMatt Brown entitled UTILITY SCALE ELECTRIC ENERGY STORAGE SYSTEM, thedisclosure of which is incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates generally to electric power storage andgeneration. More particularly, the present invention provides a systemfor potential energy storage employing electrically driven rail consists(a consist is defined herein as multiple train car elements) carryingoff loadable masses between lower and upper storage facilities forpotential energy storage by employing electrical grid power to theconsists for transport of the masses from the lower to upper storagefacility and potential energy recovery and return to the electrical gridby electromagnetic regenerative braking of the consists during transportof the masses from the upper to lower storage facility with ancillarysupport including variable and reactive power support and regulation upand down trimming capability.

2. Related Art

The electric power grid is increasingly complex and the matching ofpower generation supply with power usage is a critical element inmaintaining stability in operation. This issue is becoming morecomplicated with the addition of alternative energy generation sourcessuch as wind power and solar power which have inherent issues withconsistency of power production. The need for utility scale energystorage as a portion of the power supply grid is driven by increasingrequirements for daily load shifting and power quality servicesincluding frequency regulation, voltage control, spinning reserve,non-spinning reserve and black start. It is presently estimated thatenergy storage power requirements in the US will approach 200,000 MW forload shifting and exceed 20,000 MW for power quality service.

Electrical energy storage may be accomplished using batterytechnologies, capacitor storage systems, kinetic energy storage systemssuch as flywheels or potential energy storage systems. Batterytechnology for Lithium ion batteries, flow batteries and RechargeableSodium-Sulfur batteries (NaS) are improving but typically will provideestimated capability only in the range of 50 MW or less. Similarly,capacitive storage systems on reasonable scale only provide between 1-10MW of capability. Flywheel storage systems are also typically limited toless than 20 MW due to physical size and structural materialsconstraints.

Conventional potential energy storage devices consist of mechanicallifting devices raising weights against the force of gravity and PumpedHydro, a method that stores energy in the form of water pumped uphillagainst the force of gravity. Mechanical lifting devices are limited intheir height to a few hundred feet and therefore require large amountsof mass to store a significant amount of electric energy. This resultsin a very large cost, making these devices expensive and uneconomical.In Pumped Hydro, water is pumped from a lower elevation reservoir to ahigher elevation; the stored water is then released through turbines toconvert the stored energy into electricity upon demand. The round-tripstorage cycle efficiency losses of such systems are typically in therange of 25% and the difficulties in permitting, constructing andoperating makes pumped hydro difficult to implement. It can take morethan a decade to construct such a system.

It is therefore desirable to provide potential energy storage withcapability in the power generation range of 100-2,000 MW with highefficiency and reduced installation and capital investment requirements.

SUMMARY

The embodiments disclosed herein provide a highly efficient, utilityscale energy storage system. Large masses are transported uphill tostore energy and downhill to release it. An electrified steel railwaynetwork shuttles the masses between two storage yards of differentelevations via electric powered shuttle units containingmotor-generators combined in consists and operated by an automatedcontrol system. The exemplary embodiment incorporate a rail systemhaving upper and lower storage yards with interconnecting track betweenthe upper and lower yards and multiple control elements for configuringtrack routing in the system. Shuttle units have an electricalmotor/generator interconnected to supporting wheels and incorporate asupport structure and integral transfer mechanism for removably carryingthe masses. The motor/generators on the shuttle units are interconnectedto an electrical grid. A control system in communication with theelectrical grid, the shuttle units and the rail system control elementsexecutes a first control sequence to store energy when the electricalgrid has excess power and executes a second control sequence forproviding power to the electrical grid when additional power isrequired. The first control sequence causes selected shuttle units toretrieve masses located in the lower storage yard and, using themotor/generator as a motor drawing power from the grid, drive theselected shuttle units from the lower storage yard to the upper storageyard with the control elements configured to route the shuttle unitswhich then offload the masses in the upper storage yard. The secondcontrol sequence causes selected shuttle units to retrieve masseslocated in the upper storage yard and, using the motor/generator as agenerator, supply power to the grid by regenerative braking the selectedshuttle units from the upper storage yard to the lower storage yard withthe control elements configured to route the selected shuttle unitswhich then offload the masses in the lower storage yard.

In exemplary embodiments, the masses are stored in the upper and lowerstorage yard suspended over storage yard tracks and each shuttle unit isreceived under selected masses. The transfer mechanism incorporates asupport element carried by structure on each shuttle unit and receivedunder the mass as stored to provide roll under loading.

In exemplary embodiments, a substation is connected to the grid toreceive high voltage power and a trackside electrical distributionsystem is connected to the substation with transformers connected to theelectrical distribution system at selected intervals. Power supply railsconnect to the transformers with each power supply rail associated witha track in the rail system. Each shuttle unit includes contactors forconnection to the power supply rails and a traction control unit (TCU).The TCU incorporates rectifier/inverter circuits for power controlconnected to the motor/generator and a control board for control of therectifier/inverter circuits for acceleration, deceleration and steadystate operation of the motor/generator. A first utility siderectifier/inverter and a second motor/generator side rectifier/inverterare employed with the control board controlling reactive power in theutility side rectifier/inverter for volt-ampere-reactive (VAR)adjustment to the electrical grid.

In certain embodiments, reversing bypass connectors responsive to asignal from the control board for selectively bypassing the rectifierinverter circuits with direct connection of the motor generator forshuttle units on a selected connecting power track to the power supplyrail for synchronous operation after acceleration/deceleration of theshuttle units. Voltage adjustment in the system responsive to a utilitysignal for regulation up or regulation down is accomplished in eachshuttle unit with asynchronous operation.

The disclosed embodiments allow a method for providing utility scaleancillary services using the rail system and shuttle units connected theelectrical grid. Upon receiving a command for ancillary service, aselected set of the shuttle units is controlled for reactive power,acceleration and deceleration to interact with the electrical grid insatisfaction of the ancillary service command. If a command forancillary service is a VAR command, the shuttle units, which haverectifier/inverter circuits to provide power to the motor generator,control reactive power in the rectifier/inverter circuits for VARcontrol adjustment to the electrical grid. If the ancillary servicecommand is a regulation up/regulation down command, at least one powertrack in the connecting tracks is selected for asynchronous operationand the motor generator on shuttle units traversing the selected powertrack are controlled for regulation up or regulation down of powersupplied to or stored from the grid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective overview of an embodiment of the present energystorage system;

FIG. 2 is a perspective view of a first exemplary embodiment ofoperating consists with multiple shuttle units and storage massesemployable in an energy storage system as disclosed in FIG. 1;

FIG. 3 is a side view of one shuttle unit of the first embodiment havingengaged and elevated a mass for transport

FIG. 4 is a side view of the shuttle unit of FIG. 3 in position toengage a mass for transport;

FIG. 5 is a perspective view of operating consists with a secondexemplary embodiment of shuttle units and storage masses;

FIG. 6 is side view of one shuttle unit of the second embodiment with amass in transport position;

FIG. 7A is an end view of the shuttle unit of FIG. 6;

FIG. 7B is a partial perspective side view of the shuttle unit andtrackside components;

FIG. 8 is a perspective view of one shuttle unit of the secondembodiment with the mass in rotational transition for storage;

FIG. 9 is an end view of a shuttle of the second embodiment with themass rotated for storage;

FIG. 10A is a detailed isometric view of the rotational support systemfor mass handling on the shuttle as defined in FIG. 6;

FIG. 10B is a cross section of an exemplary transmission for use withthe drive axles:

FIG. 11A is a pictorial view of an exemplary multi-track power andreturn layout employed in an embodiment of the energy storage system;

FIG. 11B is an exemplary upper storage yard layout for the energystorage system;

FIG. 11C is an exemplary lower storage yard layout;

FIG. 11D is an exemplary layout for supplemental upper and lower storageyard expansion;

FIG. 12 is a trackside power schematic for an embodiment of the system;

FIGS. 13A-D are a flow chart of an exemplary operational scenario forthe disclosed embodiments of the energy storage system;

FIG. 14 is a shuttle unit power schematic for an embodiment of thesystem;

FIG. 15A is a flow chart of the operational characteristics for theshuttle unit power controller

FIG. 15B is a flow chart of exemplary operations for VAR support by thesystem;

FIG. 15C is a flow chart of exemplary trimming operations for regulationup or regulation down by the system.

DETAILED DESCRIPTION

Referring now to the drawings for description of various embodiments inmore detail, FIG. 1 shows an embodiment for the advanced rail energystorage (ARES) system having an upper storage yard 10, a lower storageyard 12 and connecting tracks 14 and 16. While only single power andreturn tracks are shown in FIG. 1, multiple tracks may be employeddepending on system requirements as will be described in greater detailsubsequently. Large masses 18 are transported between storage yards 10and 12 by electric powered consists 20 which are multiple unit elementshaving one or more shuttle units 22 on an electrified steel railwaynetwork 24 created by tracks 14, 16, storing or releasing energy. Theempty shuttle units (designated 22′) are returned on the electrifiedsteel railway network 24. The steel railway network incorporatesmultiple connecting track sets allowing bi-directional motion of loadedand empty shuttle units. During periods of storage or discharge acontinuous flow of electric powered shuttle unit consists carry massesbetween storage yards. The steel railway network is connected to thelocal electricity grid via wires 26 connected to an electric substation28 and distributed through trackside AC electrical distribution lines 30and transformers 32 which provide power interconnection at approximately1,060′ intervals to power supply rails or “third rails”, as will bedescribed in greater detail subsequently, which incorporate a componentof highly conductive material along their length such as aluminum orcopper to avoid resistive loss during electric power transmission. Therailway network may include storage and repair elements 35 for theshuttle units.

A selected number of shuttle units 22 in each consist 20 are electricpowered as electrified mules or slugs and are controlled by an automatedcontrol system 34 as will be described in greater detail subsequently.Each electrified mule employs undercarriage trucks, comparable to thosein current use on diesel-electric locomotives, which use reversibleelectric motor-generators as traction motors for carrying masses fromthe lower storage yard to the upper storage yard and as generators fordynamic braking while carrying masses from the upper storage yard to thelower storage yard. In this application the electric tractionmotor-generators which power the wheels are storing potential energywhile raising masses uphill in motor mode and delivering energy viageneration in dynamic braking mode while lowering masses downhill. Forthe exemplary embodiments described herein, the shuttle units employstandard railway bogies such as 3-axle radial bogies produced byElectro-Motive Diesel, Inc. as described in US Patent Publication US2010/0011984 A1 published Jan. 21, 2010 entitled Self-Steering RadialBogie. Each truck has multiple wheels to engage the steel rails of theARES system railway network and is of conventional gauge forcompatibility with common carrier rail lines.

The embodiments disclosed in FIG. 1 and FIG. 2 show shuttle units 22with bogies 36 each having multiple wheels 38 riding on rails 39 in therailway network. Each shuttle unit incorporates a support structure,described in greater detail subsequently, to carry masses 18 that may bemade of concrete (such as reinforced and/or post tensioned concrete orof reinforced and/or post tensioned heavy concrete made from orematerial such as taconite) or of any other sufficiently rigid and strongmaterial such as high-strength plastic, metal, wood and the like. Themasses can be solids fabricated from the base material such asreinforced concrete or hollow and filled with burden 42 such as dirt,rock, water, wetted sand, wetted gravel, wetted basalt, iron ore or anyother sufficiently dense material preferably produced during on-siteexcavation. For an exemplary embodiment, each mass is a reinforcedconcrete container constructed of pre-cast, post-tensioned or reinforcedconcrete panels having an outer dimension 17′ in height by 17′ in widthby 19.5′ in length. The side walls and base of the masses are 18″ thick,creating a total volume of 5,636 cubic feet. With burden atapproximately 150 lbs per cu ft and similar density of the containermaterials, total weight for each mass may approach 424 tons. Each massmay be equipped with a manifold of tubes to enable the enclosed materialto be liquefied by water or air injection allowing their beddingcontents to be easily removed and replaced in the event of the need toadjust mass weight or center of gravity or in the event wetting of thestorage medium were desirable to trim the mass density.

The shuttle units 22 are low in profile so that they can roll beneaththe filled masses which are stored in the upper and lower storage yardssuspended over storage yard tracks as will be described in greaterdetail subsequently. As shown in FIGS. 3 and 4, a storage transfermechanism for the first embodiment incorporates a lever base 50 mountedat a first end to a stanchion 52 extending from a first bogie 54 ofshuttle unit 22 with a pivot pin 56. A collapsible hinge 58 attaches thelever base proximate a second end to a second bogie 60 of the shuttleunit. In the collapsed position of the lever base 50 shown in FIG. 4,the shuttle unit 22 may roll freely under the mass 18. Extendingcollapsible hinge 58 with hydraulic ram 61 to lift the lever base 50 asshown in FIG. 3 lifts the masses off of their resting piers 62 shown inFIGS. 3 and 4 or off integral leg supports 64 as shown in FIG. 2. Thisoperation is reversibly repeated in the upper and lower storage yardsfor loading and unloading the masses. For the embodiment shown, thelever base is arcuate in shape to allow clearance of the first end atthe pin/stanchion mount in the lowered position. Pre-stressing of thebeam structure of the lever base with associated straightening of thelever base due to imposed stress upon lifting of the mass provides therequired arcuate shape in the unloaded collapsed condition. Anengagement pin 66 on the lever base is received in a mating relief 68 inthe mass 18 for securing the mass against movement on the lever baseupon extension of the collapsible hinge.

For the embodiment of FIGS. 3 and 4, piers 62 are positioned toaccommodate support of four rectangular masses with each mass supportedat one corner on an associated pier. In alternative embodiments, K-railsor similar upstanding support elements may be employed reducing thealignment tolerance requirements. In the self standing leg embodimentdisclosed in FIG. 2, having ground level support for the masses allowsaccess to the rails 39 of the storage tracks 65 in the storage yards formaintenance. Similarly, use of K-rails, movable support piers or similarmovable support structures allows maintenance access.

By having the shuttle units able to roll beneath the masses it becomespossible to pick up and deposit individual masses in sequence withprecision in the storage yards. This allows the ARES system to parkindividual masses closely together in the storage yards greatly reducingthe length of electrified rail system required for storage purposes.This feature also allows the individual masses to have greater spacingonboard the electric shuttle units thereby allowing multiple wheelbogies per mass in motion; thus creating the capability for the overalltransport of heavier masses which require less storage track. As suchthe energy storage density and economic viability of the overall systemis greatly improved.

A second embodiment for the consists employs shuttle units and carriedmasses as shown in FIG. 5. In this embodiment each consist 70incorporates four shuttle units 72. In this exemplary embodiment, two ofthe shuttle units in the consist are powered mules, as will be describedin greater detail subsequently, and two shuttle units are unpowered.Masses 74 are rectangular in horizontal section allowing a foot print ofthe mass to be peripherally supported by the structure of the shuttleunit as will be described in greater detail subsequently. As shown inFIGS. 6 and 7A, each mass 74 is carried longitudinally on the shuttleunit 72 for transport within the railway network. Each shuttle unit, forthe embodiment shown, employs two 3-axle radial bogies 76 carrying asupport structure 78. This allows for an acceptable weight loading ofapproximately 50 tons per axle. Each shuttle unit incorporates a storagetransfer mechanism described in greater detail subsequently, whichallows a mass 74 to be lifted and rotated to a lateral or transverseorientation as shown in FIG. 8. When fully rotated as shown in FIG. 9,the mass is perpendicular to the storage track 65 and is lowered by thetransfer mechanism to be supported on piers or support rails 76. Asdescribed with respect to the prior embodiment, movable K-rails employedas the support rails for mass storage allows unencumbered access to thestorage yard tracks for easy maintenance. K-rails are commonly used astraffic barriers. For the embodiments shown, the K-rails in section areapproximately 6′ wide at their base narrowing to 2′ at top width. Thetop surface of each support rail is a layer of reinforced rubbercushioning. The support rails are bedded trackside in crushed rockprimary ballast.

As with the first embodiment, the potential energy in an exemplarylarge-scale ARES system described above is stored in approximately14,000 masses, each weighing approximately 240 tons, each mass is areinforced concrete container constructed of pre-cast, post-tensioned orreinforced concrete panels having an outer dimension 13′ in height by39′ in width by 6.6′ in (track) length. The side walls and base of themasses will be approximately 18″ thick, creating a total mass volume of3,350 cubic feet. The volume of each mass will be filled with heavy rocksuch as basalt bedded in sand, preferably produced during on-siteexcavation, depending on specific locations this mixture of materialwill provide a weight of approximately 143 pounds per cubic foot. Theweight of the concrete container structure is also approximately 143pounds per cubic foot. The masses are stored perpendicular to thestorage tracks on movable reinforced concrete support rails, whichparallel the tracks in the storage yard minimizing space demands andfacilitating rapid loading onto shuttle units as previously described.Each mass may be equipped with a manifold of tubes to enable theenclosed material to be liquefied by water or air injection allowingtheir bedding contents to be easily removed and replaced in the event ofthe need to adjust mass weight or center of gravity or in the eventwetting of the storage medium were desirable to trim the mass density.In an alternate embodiment the masses are constructed of interlockinglayers of material allowing for crane removal or delivery of masses inlayers or sections. The highly rectangular aspect of these masses whichallows for their perpendicular storage over the storage tracks greatlyreduces the miles of storage track required for an ARES system of agiven capacity and when loaded and in motion provides for a significantreduction of the polar moment of inertia of the shuttle units improvingreliability and reducing wheel wear. The rectangular masses of thesecond embodiment may be sized to conform with AREMA (American RailwayEngineering and Maintenance-of-Way Association) dimensions for limitedinterchange service freight, allowing for the shipment by rail of emptymass containers for use at ARES facilities.

Returning to FIG. 5 with additional reference to FIG. 10A, each shuttleunit 72 in a 4-shuttle unit consist 70 is equipped with a transfermechanism employing multiple hydraulic rams 80 actuated by a servosolenoid, or other conventional control device, and powered by ahydraulic pump 82 on board the consist. The hydraulic pump draws itspower from the third rail. The transfer mechanism also includes ahydraulic lift 86 incorporating a rotating engagement table 87, on whichthe masses rest, positioned in the middle of the shuttle unit supportedby longitudinal structural elements 88 and transverse structuralelements 90 incorporated in support structure 78, sized as required toaccommodate the weight of the masses and any generated tipping momentsduring operation.

When the consist is positioned to pick up a first mass, the liftactuates and the engagement table is lifted and the mass is raised offthe support rails to a clearance height. The consist then moves awayfrom the stored masses until a second mass is positioned over the secondshuttle unit for pickup. While the second mass is being lifted, thefirst mass and engagement table is rotated by hydraulic rams 80 untilthe mass is parallel to the track. The mass is then lowered unto thesupport structure 78 above the two bogies of the shuttle unit. Thisoperation is repeated for loading of masses on the third and fourthshuttle units of the consist. The consist is then ready for dispatchonto a power rail.

Off-loading of masses at the arriving storage yard is accomplished byreversing the described process. The consist enters the storage trackand an end mass is lifted and rotated from the longitudinal position tothe transverse position for reduced spacing placement on the storagesupport K-rails. As the consist moves forward to place the first mass,the adjacent mass in the consist is then lifted, rotated, then loweredin sequence onto the support rails. This step is repeated for the thirdand fourth masses on the consist which then passes beneath the row ofstored masses and is then released to transition onto the return trackto the originating storage yard.

FIG. 11A shows details of an exemplary implementation of the beginningtrack sections of a power and return track system. The specific elementsof each ARES system facility will vary with its intended storage andgeneration capacity, the elevation difference between the upper andlower yards and the grade. An ARES facility with a 3,600-foot elevationdifference between upper and lower storage yards and an averageinter-yard grade of 7.5% will be able to charge or discharge at 1,000 MWwhile providing 8000 MWh of net energy storage. Such and exemplaryembodiment could incorporate the following fixed elements.

Five parallel electrified main tracks consisting of two power tracks 14a and 14 b, two return tracks, 16 a and 16 b and one standby track 17able to operate in either mode; each main track approximately 8.1 milesin length connecting between an upper and lower storage yard. Inalternative embodiments, additional power and return tracks may beemployed for sizing of the ARES system to match power requirements. Inan embodiment employing four power tracks and two return tracks, themain tracks provide a capacity for 203 or more consists to be incontinuous operation charging or discharging and returning. The consistoperating speed on a power track is approximately 35 mph with theonboard power system for the electrified shuttle units in synchronousoperation as will be described subsequently, but may be controlled at adesired alternate speed for variation in power input or output. Thesynchronous control speed allows direct connection of the tractionmotor/generators on the shuttle units to the AC trackside system withsignificant efficiency savings. The empty consist speed on the returntrack is a function of the total number of consists in the system;however an approximate returning speed would be 60-70 mph. In thisconfiguration, approximately fourteen percent of the total power tracklength is occupied by moving consists, which are spaced approximately1,300 feet apart in-motion when four tracks are employed forcharge/discharge and two for returning consists. The combined length ofthe six operational tracks between the upper and lower storage yards is48.6 miles. The standby track may substitute as either a power track ora return track as necessary to permit system maintenance and enhanceoperational reliability. The power, return and standby tracks are allfully capable of acting in either capacity and may be substituted forone another allowing for rotation during routine track maintenance andeven distribution of track wear.

An upper storage yard 10 and lower storage yard 12 are shown in FIGS.11B and 11C, for an exemplary embodiment each incorporatingapproximately sixteen 1.2 mile long storage tracks 65. Each storage yardis approximately 1.7 miles long and 800′ in width; the extra lengthallowing the individual storage tracks to be staggered into atrapezoidal footprint allowing for switching at the beginning and end ofeach track. Multiple interconnecting lines and switches are configuredto enable a loaded consist proceeding out a storage yard to be startedonto one of the main tracks every 7.4 seconds with spacing betweenconsists as indicated above. Multiple insulated power supply rails 84,as previously described, provide trackside AC power for mule shuttleunits in the consists operating on the main tracks, standby track andstorage yard tracks. These power supply rails are connected atappropriate intervals to a trackside 2,300V AC distribution system thattransmits power into or out of the consists during operation in thestorage yards and while in generation or discharge on the main tracks.FIG. 7A shows an exemplary configuration for the power supply rails 84and associated contactors 89 mounted to the structure of the poweredmules in the consist. For the embodiment shown, an upstanding support 91carrying the supply rails in a 3-phase arrangement is shown. In analternate embodiment trackside power is supplied into and out of theshuttle units via 3 kV DC power supply rails with appropriate AC powerconversion onboard the shuttle units.

Additional storage tracks may be included as deemed appropriate toprovide backup consists with rapid access to a storage yard forimmediate deployment in case of breakdowns. Additional masses as deemedappropriate may be provided to be held in reserve. The reserve shuttleunits and reserve masses may be stored on the same backup siding(s). Aspur track 93 (shown in FIG. 11A) is included to provide access from theARES facility to a common carrier rail line (to facilitate originalconstruction, delivery of shuttle units and of maintenance and repairitems). The shuttle units, are interchangeable among ARES facilities atdifferent locations in order to cost effectively accommodate periods ofpeak regional storage demand. Standard gauge bogies for the shuttleunits allows transportation over the commercial railway network to anydesired location.

FIG. 11D shows supplementary upper and lower storage yards 10′ and 12′which are nested within the upper and lower yards 10 and 12. Thisconfiguration allows the addition of greater storage capability whilemaintaining easy switch access to the power, return and standby tracksin the railway system.

For the embodiments shown, all tracks in the ARES system facility,including the storage yard track are electrified with parallel powersupply rails providing continuous AC electric supply to the shuttleunits. The tracks are heavy (136 lb./yard) head-hardened standard gaugerail. The track is laid on a reinforced heavy capacity roadbed withdirect track fixation to reinforced concrete anchors spaced atapproximately 620′ intervals, for the exemplary embodiment shown, toprevent down-slope track-creep. The roadbed matrix is comprised of amultiple sub-ballast layers, typically a rock primary ballast with ahot-mix asphalt underlayment. The storage yards contain multipleparallel storage tracks so time allowance for the dispatch of each Massis not limited by the time required for a single row of shuttle units toposition and engage their respective loads.

FIG. 12 demonstrates a trackside power system for the presentembodiment. As previously described with respect to FIG. 1, a substation28 attached to high voltage power lines transforms available power to34.5 KV. Trackside electrical distribution lines 30 distribute or returnpower along the tracks in the system represented as a power track 14 andreturn track 16 in FIG. 12. Fused disconnects 90 connect the electricaldistribution lines to transformers 32 for voltage adjustment between34.5 KV and 2300 VAC operational voltage. Circuit breakers 92 connect3-phase power supply rails 84 a or 84 b associated with each track forinterconnection to the contactors on electrified mules in the consists.For increased efficiency, power derived from braking regeneration oneither a power track or a return track is provided through a directconnection with interconnects 94 between track power supply rails foruse in providing preferred power to consists traveling uphill avoidingassociated substation and on-site transformer and transmission losses.

In broad embodiment, the present invention is a highly efficient and lowcost potential energy storage system. The rate of input and output canbe varied considerably by controlling the speed and or quantity of theelectric powered shuttle units in motion. Standard friction brakes canbe used to park the electric powered shuttle units and to stop them incase of a failure.

A computer or computers housed in the automated control system 34running supervisory control and data acquisition (SCADA) software willbe used to control the energy storage system operation. Following is adescription of computer sensors, actuators and an exemplary algorithmthat can be used to control an ARES system as described for theexemplary embodiments. This is only one example of computer sensors,actuators and process and the energy storage system operation is notlimited to these computer sensors, actuators and process.

The ARES system operates in a predetermined manner dependent on suchfactors as requirements for storing or releasing energy, the rate ofpower being stored or released, the range of ancillary services thesystem is providing to the grid, the weather conditions, and others. Ituses sensors that include but are not limited to individual consistposition, velocity, acceleration, mass position, wheel speed and slip,electric component amperage draw, electric component voltage, electriccomponent temperature, mechanical component temperature, rail switchposition and others. These sensors and communications components can behard wired or wireless with various communications systems andprotocols. The control system may use controllers that include but arenot limited to individual consist friction brakes, track switch motion,electric and electronic switches, consist mass lifting mechanisms andothers. These controllers can be electro-mechanical, pneumatic orhydraulic.

Trackside location tags 95 placed every 50 feet alongside the maintracks, as shown in FIG. 7B (attached as exemplary to the stanchions forthe power supply rails, will signal to sensors 96 on the consistsreporting on the location and speed of each consist. Using thisinformation, the SCADA system will control the motion of all shuttleunits in motion. In the storage yards, the location tags will be locatedat much closer spacing to help position the consists for mass pickup.Location tags may also be placed on the masses themselves for finalpickup positioning. Differential GPS transponders 97 on the consists, asa backup to the location sensors/location tags, can also transmit allshuttle unit locations to a real time display in the control center. Anon-site differential GPS transmitter on or near the ARES facility willbe employed to enhance the accuracy of the shuttle unit data received atthe control center. Additional sensors on each consist will monitor andcontrol rectifier/inverter function, backup battery status, motorgenerator status, lift mechanism function, brake function, trackcondition, and hydraulic fluid output under control of the SCADA system.For an exemplary embodiment, a multiplex telemetry system operatesthrough the rails capable of delivering unique commands to each consistwith a backup communication system routed to the location sensors.

The process of starting, operating and stopping the energy storagesystem can be a pre planned set of steps that the components go through.There can also be pre planned steps for changing the power in or output,removing a consist from the process for repair and others. Each step inthe process can be accomplished by a single or multiple sensors and oractuators. Additionally, each consist may be programmed to act as amember of an ad hoc meshed network system in which the consist respondsto the operational requirements being received from a control center ina pre programmed manner relative to its position relative to otherconsists and switch settings. An example of operational flow is shown inFIGS. 13A-D.

Excess grid power is detected, in step 1302 and the ARES system isengaged to store energy. Using an exemplary system with the seconddescribed embodiment and fictitious consist numbering, mass numberingand storage locations for reference purposes, consist #178 connects tothe grid and is moved to a position under mass #1584 at location 4L-128(storage track 4 lower yard storage position 128), step 1304. Theconsist is loaded in step 1306; the transfer mechanism on first shuttleof consist #178 is extended to engage mass #1584, the consist is movedone position and the transfer mechanism on second shuttle is extended toengage mass #1585, the consist is moved one position and transfermechanism on third shuttle is extended to engage mass #1586, the consistis moved one position and transfer mechanism on fourth shuttle isextended to engage mass #1587. Rail switch #L47 switches storage track#4 for uphill right of way onto a selected power track in step 1308.This loading process is sequentially repeated. For example consist #179then moves to a position under mass #1588 at location 4L-132 (track 4lower yard pylon position 132) and so on.

Consist #178 proceeds along storage track #4 onto uphill right of wayand employs grid power, step 1310. On board control accelerates theconsist to synchronous speed, step 1312, and then converts to directsynchronous operation, step 1314. The ARES system then monitors fortrimming (regulation up/regulation down requirements from the utility orISO), step 1316, and monitors for VAR requirements, step 1318. Railswitch U21 switches uphill right of way onto storage track #8 in theupper storage yard, step 1320. The on board control converts from directsynchronous operation to decelerate consist from synchronous speed, step1322. Consist #178 positions mass #1584 at location 8U-275 (track 8upper yard pylon position 275), step 1324, the consist then unloads themasses, step 1326; the transfer mechanism on first shuttle of consist#178 is extended to off load mass #1584 at location 8U-275, the consistis moved one position and transfer mechanism on second shuttle isextended to off load mass #1585, the consist is moved one position andtransfer mechanism on third shuttle is extended to off load mass #1586,the consist is moved one position and transfer mechanism on fourthshuttle is extended to offload mass #1587. A determination is then madewhether to store #178 at upper yard or return to lower yard foradditional mass transportation, step 1328. If returned, rail switch U21switches storage track #8 to downhill right of way on a selected returntrack, step 1330 and consist #178 descends from track #8 to lower yard,step 1332. If stored, switch U21 switches storage track #8 to upperstorage yard siding, step 1333 and consist #178 transitions off track #8to upper storage yard siding, step 1334. Depending on storage railrequirements, the consist may be stored in position under the masses.The steps are sequentially repeated for additional storage masses untilpower storage requirements communicated by the utility or ISO arecompleted.

When a power demand received from the utility or ISO, step 1336, switchU21 connects upper storage yard siding to upper storage track #8, andconsist #178 connects to the grid step 1338, and is moved to a positionunder mass #1587 at location 8U-275 (track 8 upper yard pylon position275) and loaded, step 1340. For loading the consist the transfermechanism on first shuttle of consist #178 is extended to load mass#1587 at location 8U-275, the consist is moved one position and transfermechanism on second shuttle is extended to load mass #1586, the consistis moved one position and transfer mechanism on third shuttle isextended to load mass #1585, the consist is moved one position andtransfer mechanism on fourth shuttle is extended to load mass #1584.Rail switch #U21 switches track #8 for downhill right of way, step 1344.Consist #178 proceeds along track #8 onto downhill right of way andemploys bogie generators for speed control transferring generated powerto grid while reaching lower yard, step 1346. This operation is repeatedsequentially for additional consists. Consist #177 moves to a positionunder mass #1583 at location 8U276 and so on.

On board control accelerates consist #178 to synchronous speed and thenconverts to direct synchronous operation, step 1348. The system thenmonitors for trimming (reg up/reg down requirements), step 1350 andmonitors for VAR requirements, step 1352. Upon approaching the lowerstorage yard, rail switch L47 switches downhill right of way onto lowerstorage track #4, step 1354. On board control converts from directsynchronous operation to decelerate consist from synchronous speed, step1356. Consist #178 positions mass #1587 at location 4L-128, step 1358.The consist then offloads the masses step 1360; the transfer mechanismon first shuttle of consist #178 is extended to off load mass #1587 atlocation 4L128, the consist is moved one position and transfer mechanismon the second shuttle is extended to off load mass #1586, the consist ismoved one position and transfer mechanism on the third shuttle isextended to off load mass #1585, the consist is moved one position andthe transfer mechanism on fourth shuttle is extended to offload mass#1584. A determination is then made whether to store consist #178 atlower yard or return to upper yard for additional mass transportation,step 1362. If returned, rail switch U21 switches track #8 to uphillright of way on a selected return track, step 1364 and consist #178ascends from storage track #8 to the upper yard, step 1366. Ifmaintained in the lower storage yard, the consist position is eithermaintained or the storage track is switched to the siding, step 1368 andthe consist is moved onto the siding, step 1370.

Returning to FIG. 10A, two of the shuttle units in each consist, eachwith two 3-axle radial bogies 76 providing a total of six axles 101, arepowered by AC buried permanent magnet synchronous motor-generators 102to generate enough tractive effort to brake the consist down hill. Thesesynchronous motor-generators replace the asynchronous motor-generatorscurrently used in the railroad industry. The remaining shuttle units arenot powered by traction drive axles and are spaced alternatelyin-between mules in a consist to achieve maximum adhesion from loadedmasses during loading and unloading. In alternative embodiments, thetotal number of powered axles and/or shuttle units may be varieddepending on operational requirements.

The motor-generators' torque is transmitted to and from the drive axlesvia a mechanical gearbox 104 and the speed of the drive wheels isdetermined by the number of poles in the motor generator, the fixed gearratio of the gearbox and the drive frequency of a traction control unit(TCU) 106 provided for each mule as will be described in greater detailsubsequently.

As shown in FIG. 10B, operation of the consists synchronously with thetrackside distribution system is enhanced by use of transmissionelements in gearbox 104. A dog clutch 105 operating between gear trains107 a and 107 b allows selection for a first synchronous speed for powertrack operation of the shuttle units in a loaded consist and a secondsynchronous speed for return operation of the consists in an unloadedstate.

The speed of the consist is determined by the TCU which, in response tocommands from the control center SCADA system, determines the frequencyat which the synchronous motor/generators operate, and thus the speed ofthe shuttle units in the consist.

For the embodiment disclosed, the two shuttle units which are powered aselectrified mules in a consist are each riding on two pairs of radial3-axle diesel-electric locomotive bogies. This configuration allows eachcar six axles and provides for a loaded consist wheel loading of 50,000lb (50 tons per axle). For an exemplary implementation of the describedembodiments, each regenerative traction motor/generator for thedescribed embodiment has a peak power capacity of 1.25 MW coupled to theaxle with a reducing transmission gearbox as previously described. At 35mph on a 7.5% grade each motor/generator-equipped axle will generate anet output to the grid (after system efficiency losses) of 0.74 MW fromthe potential energy of the masses carried by each consists in motion.The peak mule axle power requirement is based on the power of the massof the consist in motion at 35 mph (12.5 MW) divided by the number ofpowered axles per consist (12) times a reserve power of 20% foracceleration/deceleration (1.2).

The net mule axle power to grid may be calculated as the power of theloaded consist in motion at 35 mph (12.5 MW) divided by the mass toconsist weight ratio (1.26) divided by the number of powered axles perconsist (12) times the one-way system efficiency loss (0.89); equaling0.74 MW

Each consist of the exemplary embodiment, which is a two mule plus twounpowered shuttle unit train providing 12 powered axles, will generateapproximately 8.8 net megawatts power when synchronized directly intothe grid at a speed of 35 mph on a 7.5% grade. Variations in gradewithin a particular ARES facility are accommodated by sizing themotor/generator unit and/or gear box on each axle to respond to themaximum slope output plus a reserve power component for acceleration ordeceleration adequate for such slope. Variations in slope at differentARES sites may be accommodated by having more un-powered axles if thepeak grade is shallower or increasing the number of powered axles if theslope is steeper. Alternately, variations in slope at different ARESsites may be accommodated by changing the ratio of mules to unpoweredshuttle units in a consist; or by a combination of the two means.

Using the case of a 1,000 MW ARES facility at full-rated power therewill be 1,326 axle mounted motor/generators onboard 227 mules in 114mass loaded consists in motion on the six power tracks at a given time.The other 106 consists are either returning to the loaded storage yardto pick up their next load of masses or in process of sequencing theirloading. Having the unloaded consists return for loading on the returntracks at approximately twice the loaded control speed (by atransmission gear ratio change in the current embodiment to allowsynchronous return operation) on the power tracks greatly reduces systemcapital cost with minimal impact on efficiency.

Variations in grade on a given system may be accommodated by sizing themotor/generators to the power requirement for the steepest section ofrail and reducing the number of engaged motor/generators on a givenshuttle unit or consist so that the power requirement matches thepotential energy of the track grade at a given point. This allows eachconsist to maintain a set grid-synchronization speed without loosingdirect-synchronization. In effect throttling the consists by varyingnumber of its on-line motor/generators to match the track grade ratherthan changing the control frequency of its motor/generators.

To provide the required operational characteristics in the poweredshuttle units an onboard power system as shown in FIG. 14 is employed.The trackside power system (for the embodiments shown being 3-phase 2300VAC) is connected to the electrified shuttle unit or mule through thespaced main circuit breakers 92 to power supply rails 84. Contactors 89on the shuttle unit connect to the traction control unit (TCU) 106. Mainline contactors 107 controlled by the TCU control board 108, describedin greater detail subsequently, interconnect to the power supply railcontactors with power conditioning through an AC line filter 110 to afirst utility side 3-level active rectifier/inverter 112. For theembodiments shown, an insulated gate bipolar transistor (IGBT) circuitis employed. A second generator side 3-level active rectifier/inverter114 transfers power to (or from) the motor/generators 102. A buspre-charge circuit 116 also commanded by the control board is provided.Current sensors 120 a and 120 b and voltage sensors 122 a, 122 b and 122c are employed by the control board for sensing and control of thetrackside power system side of the rectifier inverters and currentsensors 126 a and 126 b and voltage sensors 128 a, 128 b and 128 c areemployed by the control board for sensing and control of themotor/generator power. The control board provides acceleration,deceleration and trimming control of the motor/generators as will bedescribed in greater detail subsequently.

Reversing bypass contactors 130 are provided for direct connection ofthe motor/generator to the trackside power system for synchronousoperation at the predetermined control speed for the shuttle unit.Acceleration of the shuttle unit to the control speed is accomplishedthrough the IGBT rectifier/inverter circuits at which time, absenttrimming control requirements, the control board engages the appropriatereversing bypass contactors for synchronous operation. When required,the control board reengages the IBGT rectifier/inverter circuits,disconnecting the reversing bypass contactors, for deceleration of theshuttle unit or grid trimming requirements as will be described ingreater detail subsequently.

Control interconnection by the SCADA software in the control center isaccomplished with each shuttle unit control board as previouslydescribed. Operational control of the shuttle unit is accomplished bythe TCU control board 108. The control board decouples real power fromreactive power for both the generator side rectifier/inverter and forthe utility side rectifier/inverter. The decoupling is accomplished byusing stationary to rotating transformations as is well known in theliterature. In the generator side rectifier/inverter 114 (shown in FIG.14), the reactive power is aligned with the direct axis of thegenerator. In the utility side rectifier/inverter 112 (shown in FIG.14), the real power axis is aligned with the utility voltage, where asthe reactive power component is 90 degrees out of phase with the utilityvoltage. The decoupling of the real and reactive power allowsacceleration and deceleration rates, and shuttle car power rates to becontrolled separately and independently from the reactive power providedby the shuttle unit. This is true even at zero speed and zeroacceleration, where the real power is zero, but the reactive powerremains selectable and available for utility support.

As shown in detail in FIG. 15A for control of each of therectifier/inverters 112, 114, three phase voltages, Va, Vb and Vc(scaled as required) from voltage sensors 128 a, 128 b and 128 c arereceived in a first phase converter 140 which provides two phase voltageoutputs Vx and Vy. A phase angle calculator 142 provides phase angle θ(calculated as θ=tan⁻¹(Vx/Vy)) to a first stationary to rotatingtransformer 144 which provides output of a real voltage component Vdfand an imaginary voltage component Vqf. Similarly, three phase currentvalues ia, ib and is are derived from the current sensors 126 a and 126b as input to a second converter 146 which provides two phase currentoutputs Ix and Iy. A second phase angle calculator 148 provides phaseangle θ (calculated as θ=tan⁻¹(Ix/Iy)) to a second stationary torotating transformer 150 which provides output of a real currentcomponent Id and an imaginary current component Iq. Based onacceleration/deceleration requirements or other system requirements aswill be described in greater detail subsequently, the control centerSCADA provides a real power command (designated id*) which is receivedin a first summer 152 in an inverter rectifier controller 154 whichreceives the id output from the second stationary to rotatingtransformer 150. A reactive power command (designated iq*) is providedby the SCADA to a second summer 156 in the rectifier/inverter controllerwhich receives the iq output from the second stationary to rotatingtransformer. The summed real power component is provided to a firstcompensator 158 and the summed reactive power component is provided to asecond compensator 160. Output of the first compensator is provided to asummer 162 receiving Vdf from the first stationary to rotatingtransformer to provide a real voltage command Vd* and output of thesecond compensator is provided to a summer 164 receiving Vqf from thefirst stationary to rotating transformer to provide a reactive voltagecommand Vq*. Vd* and Vq* are provided as inputs to a vector modulator166 which provides digital switching signals SA, SA inverse, SB, SBinverse and SC, SC inverse to the rectifier/inverters for power control.The rectifier/inverter controller for the utility siderectifier/inverter 112 receives both real and reactive power commandsfrom the SCADA while the rectifier/inverter controller for the generatorside rectifier/inverter 114 has a reactive power command set to zero.

In the presently disclosed embodiments, the rectifier/inverters arepartially rated based on the motor/generator requirements to allow useof the combined IGBT reactive power control of all powered shuttle unitsin the system to Voltage-Ampere Reactive (VAR) power support to theutilities or independent system operators (ISOs) connected to the ARESsystem. At least one IGBT in each shuttle unit is connected to the highvoltage transmission system through the onboard and trackside electricalsystems as shown and described with respect to FIGS. 12 and 14. Realpower commands (P component) from the TCU control board provide fornecessary acceleration and deceleration operations of the shuttle units.The reactive power (Q component) available in the rectifier/inverterIGBTs can be controlled for reactive power input/absorption from thehigh voltage system as described above. For all shuttle units notproducing any real power (stopped awaiting loading or transit) theentire power capability of the IGBTs in the TCU is available forreactive power. Upon command, reactive current (out of phase with thevoltage input) directed through the rectifier/inverter IGBTs by thecontrol board may be employed to create a large influence on the voltagein the electrical grid system. Voltage measurement and VAR commandinputs may be derived from electrical grid control center voltagemeasurement at desired locations geographically separated from the ARESsystem.

For the exemplary embodiments, to allow VAR control even with 100% theIGBTs in operation for acceleration/deceleration or operating selectedshuttle units asynchronously, inverters of approximately 4% greatercapacity are employed thereby allowing 25% of rated power availabilityfor reactive power control in response to VAR requests/requirements.

The VAR command can be generated in one of three practical ways. Thefirst includes where the energy storage system simply commands a VARlevel. This may be varying or fixed, and is often set at zero to operatethe system at unity power factor. In the second approach VAR levels arecommand by an external operator, often the grid transmission systemoperator. This operator will manually command different VAR levels overthe course of a day or seasonally as required. The third approach is toclose a voltage regulating loop where a voltage setpoint is determinedfor the operating plant and this is compared against the actualoperating voltage. The difference between these two levels creates anerror signal which can then be used to command VAR's. The SCADA systemoperating in the automated control system as shown in FIG. 14incorporates this regulation capability for the embodiments described.In this way a common or individual command can be sent to a selectednumber of shuttle unit rectifier/inverters necessary to accomplish therequired VAR adjustment.

The VAR command is processed by the shuttle unit rectifier/inverter asshown in FIG. 15B. A VAR level command is received, step 1502, in theARES control system from the electrical grid control center. The SCADAdetermines the number of shuttle units which are stationary, step 1504,and issues a command to the control boards in those shuttle units formaximum reactive power change up to the total VAR required, step 1506.The control boards in the commanded shuttle units rectifier/inverterunits in those shuttle units issue Iq* commands for full reactive power,step 1508, to be produced by the utility side rectifier inverter. Ifadditional VAR is needed beyond that which can be provided by thestationary shuttle units, step 1510, the SCADA determines real powerlevels on each operating shuttle unit, step 1512, and commands reactivepower, up to the full rated power of the rectifier/inverters, asdescribed above, for the shuttle units in motion, step 1514, up to thetotal VAR required. The control board in each shuttle unit commanded bythe SCADA issues Iq* commands up to the full rated power consistent withthe Id* commanded for real power in operation of the shuttle unit, Step1516.

Similarly, while greatest efficiency in the overall ARES system can beobtained with synchronous operation of the electrified shuttle units onthe power tracks, grid regulation up or regulation down and trimming ofthe power being stored or generated can be accomplished by operatingselected shuttle units asynchronously with the TCU, as described withrespect to FIGS. 14 and 15A, driving or braking the motor generatorunits at specific desired power. Dedication of one or more selectedpower tracks, as required for use in providing the amount of reg up/regdown or trimming needed, via asynchronous operation of the consists onthe selected rail(s) allows speed of all consists on a given rail to becontrolled while maintaining separation between consists in motion andfor sequencing into and out of the storage yards. Maintaining theremaining power tracks in a synchronous operation mode retains thehigher overall efficiency for remaining powered shuttle units in thesystem.

During generation operation of the system, rapid regulation downrequirements will require initial additional braking of consists on theselected power track resulting in a power surge. To avoid placing thissurge on the grid, the trackside power system as shown in FIG. 12 allowsthe power to be absorbed by SCADA command to the returning shuttle unitsto increase speed thereby incurring greater energy usage. Use ofreturning consists for absorbing any power surge allows immediateregulation down commands to be implemented without impact regardless ofthe operational status of the ARES system.

Operation for regulation up or regulation down and trimming is shown inFIG. 15C. When a regulate command is received, step 1550, from theelectrical grid control center of a contracting utility or ISO, adetermination is made if one power track is operating in theunsynchronized mode, step 1552. If not, the SCADA orders consists on aselected track to switch to rectifier/inverter operation, step 1554.After switching, or if one power track was already operating in anunsynchronized mode, the SCADA issues commands to the consists on theselected track to accelerate or decelerate on a preprogrammed profile,step 1556, wherein power consumption variation equals the commandedregulation up or regulation down. In a regulation down request wheredeceleration would otherwise create a spike in power consumption forthat track, interconnection of the power tracks as previously describedallows the excess power to be employed for powering returning shuttleunit consists on the return track. The consists then resume a constantspeed operation on rectifier inverter power at the altered speed for thedesired power consumption. If insufficient regulation up or regulationdown is achieved by converting one power track to asynchronousoperation, the SCADA will direct consists on a second power track toconvert to rectifier/inverter power.

Trimming operations are accomplished within the ARES system to providespecific output or energy storage by adjusting one or more tracks inasynchronous operation for specific power consumption by the consists.Longer term trimming adjustments may be accommodated by varying thedispatch rate of consists on a given power track.

The present embodiments as described provide capability for powerstorage and supply as well as ancillary services such as VAR, regulationup and regulation down in a single system.

While the foregoing written description of the invention enables one ofordinary skill to make and use what is considered presently to be thebest mode thereof, those of ordinary skill will understand andappreciate the existence of variations, combinations, and equivalents ofthe specific embodiment, method, and examples herein. The invention istherefore not limited by the above described embodiment, method, andexamples, but by all embodiments and methods within the scope and spiritof the invention as claimed.

1. An energy storage system comprising: a rail system having upper andlower storage yards with interconnecting track connecting the upper andlower yards and a plurality of control elements for configuring trackrouting in the system; a plurality of shuttle units having an electricalmotor/generator interconnected to supporting wheels, said shuttle unitsfurther having a support structure and integral transfer mechanism forremovably carrying masses; means for electrical interconnection of themotor/generators to an electrical grid; a control system incommunication with the electrical grid, the plurality of shuttle unitsand the rail system control elements and having means for executing afirst control sequence to store energy when the electrical grid hasexcess power and means for executing a second control sequence forproviding power to the electrical grid when additional power isrequired, said first control sequence causing selected shuttle units toretrieve masses located in the lower storage yard and using themotor/generator as a motor drawing power from the grid to drive theselected shuttle units from the lower storage yard to the upper storageyard, said control elements configured to route the selected shuttleunits, and causing the selected shuttle units to offload the masses inthe upper storage yard; said second control sequence causing selectedshuttle units to retrieve masses located in the upper storage yard andusing the motor/generator as a generator supplying power to the grid byregenerative braking the selected shuttle units from the upper storageyard to the lower storage yard, said control elements configured toroute the selected shuttle units, and causing the selected shuttle unitsto offload the masses in the lower storage yard.
 2. The energy storagesystem of claim 1 wherein the masses are stored in the upper and lowerstorage yard suspended over storage yard tracks and each shuttle unit isreceived under selected masses and the transfer mechanism comprises asupport element carried by structure on each shuttle unit and receivedunder the mass as stored.
 3. The energy storage system of claim 2wherein the transfer mechanism lifts and rotates the mass from asuspended storage position.
 4. The energy storage system of claim 1wherein the means for electrical interconnection comprises: a substationconnected to the grid to receive high voltage power; a tracksideelectrical distribution system connected to the substation; a pluralityof transformers connected to the electrical distribution system atselected intervals; and, a plurality of power supply rails connected tothe transformers, each power supply rail associated with a track in therail system.
 5. The energy storage system of claim 4 wherein each of theplurality of shuttle units further comprises: contactors for connectionto the power supply rails; a traction control unit (TCU) includingrectifier/inverter circuits for power control connected to themotor/generator a control board for control of the rectifier/invertercircuits for acceleration, deceleration and steady state operation ofthe motor/generator.
 6. The energy storage system of claim 5 wherein theTCU further comprises: reversing bypass connectors responsive to asignal from the control board for selectively bypassing the rectifierinverter circuits with direct connection of the motor generator to thepower supply rail for synchronous operation.
 7. The energy storagesystem of claim 4 wherein the rectifier/inverter circuits comprise afirst utility side rectifier/inverter and a second motor/generator siderectifier/inverter and the control board further comprises means forcontrolling reactive power in the utility side rectifier/inverter forVAR adjustment to the electrical grid.
 8. The energy storage system ofclaim 4 wherein the control system includes means for signaling voltageadjustment in the system responsive to a utility signal for regulationup or regulation down and the TCU in each shuttle unit is responsive tosaid adjustment signals from the control system for asynchronousoperation.
 9. The energy storage system of claim 8 wherein theinterconnecting track comprises a plurality of power tracks and at leastone return track, at least one of said plurality of power tracksselected for asynchronous operation of shuttle units on the at least oneselected track responsive to the voltage adjustment signaling by thecontrol system.
 10. The energy storage system of claim 1 wherein theintegral transfer mechanism comprises: a lever base mounted at a firstend to a stanchion extending from a first bogie of each shuttle unitwith a pivot pin; a collapsible hinge attached to the lever baseproximate a second end to a second bogie of the shuttle unit; said hingemovable from a first collapsed position of the lever base wherein theshuttle unit may roll freely under a selected mass, to a second extendedposition to lift the lever base wherein the mass is lifted from astorage position.
 11. The energy storage system of claim 1 wherein theintegral transfer mechanism comprises: multiple hydraulic rams; ahydraulic lift incorporating a rotating engagement table positioned inthe middle of the shuttle unit, said lift extendible from a firstposition to a second position to lift a mass from a storage position,said hydraulic rams movable from a first position to a second positionto rotate the engagement table aligning the mass longitudinally with theshuttle unit and said lift retractable to the first position, said liftfurther extendible from the first position to the second position withthe mass on the engagement table, said hydraulic rams movable from thesecond to the first position for orienting the mass transverse to theshuttle unit and said lift retractable to the first position for seatingthe mass in a storage location.
 12. The energy storage system of claim 1further comprising a second plurality of unpowered shuttle unitsselectively engaged to the first plurality of shuttle units formingconsists with powered and unpowered shuttle units.
 13. A method forutility scale energy storage comprising: providing a rail system havingupper and lower storage yards with interconnecting track connecting theupper and lower yards and a plurality of control elements forconfiguring track routing in the system; providing a plurality ofshuttle units having an electrical motor/generator interconnected tosupporting wheels, said shuttle units further having a support structureand integral transfer mechanism for removably carrying masses;connecting the rail system to an electrical grid; upon receiving acommand for energy storage, controlling a selected set of the pluralityof shuttle units to each load a mass from a selected storage track inthe lower storage yard; connecting the storage track to a power track;driving the motor/generator on each shuttle unit to lift the mass up thepower track to the upper storage yard; controlling the selected set ofshuttle units to unload the masses to a selected storage track in theupper storage yard; upon receiving a command for energy return,controlling a selected set of shuttle units each to load a mass from aselected storage track in the upper storage yard; connecting the storagetrack to a power track; braking the motor/generator on each shuttle unitto carry the mass down the power track to the lower storage yard;controlling the shuttle unit to unload the mass to a selected storagetrack in the lower storage yard.
 14. The method of claim 13 whereinconnecting the system to an electrical grid includes providing atrackside power system including power supply rails associated withtracks in the rail system, and wherein providing a plurality shuttleunits further comprises providing the shuttle units withrectifier/inverter circuits to provide power to the motor generator andwherein driving the motor/generator further comprises: accelerating themotor generator to a synchronous operating speed; bypassing therectifier/inverter circuits; directly connecting the motor/generator tothe supply rail for synchronous operation.
 15. The method of claim 14wherein providing a rail system includes providing a plurality of powertracks intermediate the upper and lower storage yards and whereindriving the motor/generator further comprises: selecting at least onepower track for asynchronous operation; and controlling the motorgenerator on shuttle units traversing the at least one power track fortrimming and regulation up or regulation down of power supplied to orstored from the grid.
 16. The method of claim 15 further comprising:interconnecting the power supply rails in all tracks in the system;absorbing power from the motor/generators for transient control duringregulation down while supplying power to the grid by compensating powerto returning shuttle units through the interconnected power supplyrails; and powering shuttle units in motor mode from returning shuttleunits in generation mode.
 17. The method of claim 13 wherein providing aplurality shuttle units further comprises providing the shuttle unitswith rectifier/inverter circuits to provide power to the motor generatorand further comprising: controlling reactive power in therectifier/inverter circuits for VAR control adjustment to the electricalgrid.
 18. The method of claim 14 wherein synchronization is maintainedby varying selected axles to be powered responsive to varying trackgrade.
 19. A method for utility scale ancillary services comprising:providing a rail system having upper and lower storage yards with aplurality of interconnecting tracks connecting the upper and lower yardsand a plurality of control elements for configuring track routing in thesystem; providing a plurality of shuttle units having an electricalmotor/generator interconnected to supporting wheels and carrying masses;connecting the rail system to an electrical grid; upon receiving acommand for ancillary service, controlling a selected set of theplurality of shuttle units for reactive power, acceleration anddeceleration to interact with the electrical grid in satisfaction of theancillary service command.
 20. The method as defined in claim 19 whereinthe command for ancillary service is a VAR command and further whereinproviding a plurality shuttle units further comprises providing theshuttle units with rectifier/inverter circuits to provide power to themotor generator and further comprising: controlling reactive power inthe rectifier/inverter circuits for VAR control adjustment to theelectrical grid.
 21. The method of claim 19 wherein the ancillaryservice command is a regulation up/regulation down command and furthercomprising: selecting at least one power track for asynchronousoperation; and controlling a motor generator on shuttle units traversingthe at least one power track for regulation up or regulation down ofpower supplied to or stored from the grid.